1. Field of the Invention
The present invention relates to a scanning mechanism of a scanning probe microscope.
2. Description of the Related Art
A scanning probe microscope (SPM) is a scanning microscope that mechanically scans a mechanical probe by a scanning mechanism to obtain information of a sample surface. The scanning probe microscope is a generic term for a scanning tunneling microscope (STM), an atomic force microscope (AFM), a scanning magnetic force microscope (MFM), a scanning near field optical microscope (SNOM), and the like. The scanning probe microscope raster-scans the mechanical probe and a sample relatively in the X and Y directions to obtain surface information of a desired sample region through the mechanical probe, and map and display it on a monitor TV.
Above all, the AFM is a most popular apparatus, and includes, as main machine mechanisms, a cantilever having a mechanical probe at its free end, an optical displacement sensor to detect the displacement of the cantilever, and a scanning mechanism to relatively scan the mechanical probe and a sample. As the optical displacement sensor, an optical lever type optical displacement sensor is employed most widely because of its simple arrangement and high displacement detection sensitivity. The optical lever type optical displacement sensor applies a beam having a diameter of several μm to several ten μm to a cantilever. A change in the reflection direction of the reflected beam depending on the warp of the lever is detected by a two-segments detector or the like. The operation of the mechanical probe at the free end of the cantilever is detected and output as an electrical signal. While the scanning mechanism is controlled in the Z axis direction to keep this output constant, the scanning mechanism is similarly scanned in the X and Y axes directions to map and display the uneven state of a sample surface on the monitor of a computer.
When observing a biological sample in liquid, the AFM is generally combined with an inverted optical microscope. This is because the inverted optical microscope observation is effective not only when obtaining the finding of a sample, but also when positioning the cantilever at a specific portion of the sample. For such a purpose, a lever scan type AFM to scan the cantilever in the X, Y, and Z axes directions is often used so as to cope with various biological samples and sample substrates.
A related art of a lever scan type AFM that is used in liquid is disclosed in U.S. Pat. No. 8,087,288.